Liquid levels within containers, bottles, vials and similar holders utilized within the healthcare, industrial and numerous other industries often require non-invasive monitoring. A common example where such monitoring is required in the healthcare industry is in vaccine vials. Vaccine vials typically hold between 5 to 10 ml of liquid or vaccine therein. With a representative dosage of 0.5 ml, it would be beneficial to the medical practitioner to know whether the vaccine vial had enough liquid available to accommodate another 0.5 ml dose or whether a replacement vaccine vial should be ordered from a pharmacy or the like. Such monitoring could also be used to pre-order vaccine vials based on a typical amount of vaccine used in a given period.
In order to meet the needs of such monitoring requirements, a liquid level monitoring apparatus needs to be non-invasive and able to determine a liquid level with sufficient resolution to distinguish between a liquid level of 2.49 ml and 1.99 ml. Such an apparatus further needs to be able to monitor more than one vaccine vial at a time whether in a serial or parallel manner, and should not require any modification to the containers being monitored so as to accommodate as many industries as practical.
Since support trays are often used in a medical setting to support multiple vaccine vials containing the same or different vaccines, it would be beneficial if the amount of vaccine, i.e., the liquid level, in each of the multiple vaccine vials be could ascertained while positioned on the support trays. This would provide a medical practitioner the desired information concerning the amount of vaccine in a given vial in an economic and timely manner. In other words, it would be desirable for the medical practitioner to be able to either have the liquid levels available at any point, upon request, or at a designated time. Monitoring in this manner could be done for each of the vaccine vials essentially simultaneously or at least serially but within a very minimal amount of time.
Various liquid level monitoring apparatus are well known in the prior art. One such apparatus, for example, utilizes a capacitive probe attached with adhesive to a wall of a holding container. While affective in determining liquid levels, the use of such a probe to monitor a plurality of containers would require either the use of multiple probes at a considerable expense or for someone to physically remove the probe from one container and subsequently re-adhere the probe to the next in line container. This process would necessarily need to be repeated for each container each time liquid levels are desired to be known. Clearly, neither scenario seems workable or practical especially in today's real-time, cost conscious health care environments.
Even more, the above-referenced probe is by definition invasive. The probe must be inserted into the liquid. Further, the structure of the probe makes its ability to accurately determine a liquid level dependent on a thickness of a wall of the container. If the walls of the container are too thick, for instance, the probe may not be able to determine the liquid level with sufficient accuracy. In other words, the thickness of the container wall could cause only partial penetration in the container and not throughout the bulk of the liquid resulting in a lesser sensitivity than what may be required. This could lead to inaccurate liquid level determinations.
Other prior art apparatus are known to utilize slow-wave structures to measure liquid level and rely on the confinement of electromagnetic energy in a small volume. In one such apparatus, an electrodynamic element is placed outside of a container. However, fields generated by the electrodynamic element attain only partial penetration due to this positioning and do not penetrate through the bulk of the liquid. As a result, the apparatus is unlikely to provide consistent monitoring or a sufficient level of sensitivity in many applications.
Accordingly, a need exists for an apparatus and related method for non-invasively sensing liquid levels in one or more containers in environments where it is desirable for the content of the containers not to be touched by a probe or the like. In addition, the apparatus would preferably not require a specialized container in order to facilitate measurement of the liquid levels but would provide the ability to monitor the liquid level in any container irrespective of size or shape. Even more, the apparatus would be able to monitor and determine liquid levels in multiple containers without the need for multiple probes or devices, or for human intervention to move the apparatus from one container to another. All of the said features are provided by the following invention. Naturally, any improvements along such lines should contemplate good engineering practices, such as simplicity, ease of implementation, unobtrusiveness, stability, etc.